CaseRegister

Supports

• Ruby 1.8 ~ 2.7

Installation

gem 'case_register'

And then execute:

$ bundle

Or install it yourself as:

$ gem install case_register

Usage

Refactor case statements

Take the examples from this article. Let you have a method like this:

def output(data, format)
  case format
  when :html
    return "<p>#{data}</p>"
  when :text
    return data
  when :pdf
    return "<pdf>#{data}</pdf>" # pseudocode -- obviously not valid PDF output
  else
    raise ArgumentError, "Invalid format (#{format})."
  end
end

output('Hi', :html)
# => "<p>Hi</p>"

You can refactor it by using a hash table to map the input, like what the article says.

Or use CaseRegister to register cases. Then, you are able to invoke the case directly without using switch-statements.

class MyFormatter
  include CaseRegister

  def initialize(text)
    @text = text
  end

  register_case(:pdf){ "<pdf>#{@text}</pdf>" }
  register_case(:text){ @text }
  register_case(:html){ "<p>#{@text}</p>" }
end

MyFormatter.new('Hi').invoke_case(:html)
# => "<p>Hi</p>"

Isolate methods

Let you have an api that allow the frontend to pass params to determetine which information it wants.

Since you have to use send to call the methods in user model dynamically, it will cause security issues if you do not use a whitelist to limit the methods it can access.

class User < ApplicationRecord
  def money_info
    { value: money, rate: gain_money_rate }
  end

  def notification_info
    { msg_count: new_msgs_count, last_recieved_at: last_recieved_at }
  end
end

class UserController
  METHOD_WHITE_LIST = [:money_info, :notification_info]

  def refresh
    result = params[:needs].slice(METHOD_WHITE_LIST).index_with{|method| current_user.send(method)  }
    render json: result 
  end
end

You may use if-statements or switch-statments to map the input to the desired method. But you will find you repeat writing similiar things and it seems redundant.

class UserController
  def refresh
    result = {}
    result[:money_info] = current_user.money_info if params[:needs][:money_info]
    result[:notification_info] = current_user.notification_info if params[:needs][:notification_info]
    # ...

    render json: result 
  end
end

In this case, you can use CaseRegister to DRYing up and isolate the methods to prevent unsafely calling send, which can access all the methods defined in the model.

class RefreshHelper
  include CaseRegister

  def initialize(user)
    @user = user
  end

  register_case 'money_info' do
    { value: @user.money, rate: @user.gain_money_rate }
  end

  register_case 'notification_info' do
    { msg_count: @user.new_msgs_count, last_recieved_at: @user.last_recieved_at }
  end
end

class UserController
  def refresh
    helper = RefreshHelper.new(current_user)
    result = params[:needs].index_with{|need| helper.invoke_case(need) }
    render json: result 
  end
end

Check if a case is registered

Something, you may want to check if a case is valid or not, and return error message if not.

It can be accomplish by using may_invoke_case? method. See the following example:

class UserController
  def refresh
    helper = RefreshHelper.new(current_user)
    invalid_needs = params[:needs].select{|need| !helper.may_invoke_case?(need) }
    return render json: { invalid_needs: invalid_needs } if invalid_needs.any?
    # ...
  end
end

Development

After checking out the repo, run bin/setup to install dependencies. Then, run rake test to run the tests. You can also run bin/console for an interactive prompt that will allow you to experiment.

To install this gem onto your local machine, run bundle exec rake install. To release a new version, update the version number in version.rb, and then run bundle exec rake release, which will create a git tag for the version, push git commits and tags, and push the .gem file to rubygems.org.

Contributing

Bug reports and pull requests are welcome on GitHub at https://github.com/khiav223577/case_register. This project is intended to be a safe, welcoming space for collaboration, and contributors are expected to adhere to the Contributor Covenant code of conduct.

License

The gem is available as open source under the terms of the MIT License.